PURPOSE: To determine the nutritional and metabolic roles of selenium, vitamin E and cystine in prevention of exudative diathesis, encephalomalacia, muscular dystrophy and pancreatic fibrosis in chicks; to examine the transport and dispersion of vitamin E in adipose tissues, in brain and in phospholipids of muscle, liver and pancreas of chicks and the influence of dietary selenium upon vitamin E transport and distribution; to determine if peroxides are formed in brain or other parenchymatous tissues under conditions of severe deficiencies of both vitamin E and selenium; to determine the effects of severe deficiencies of vitamin E and selenium upon mitochondrial, microsomal and lyososmal membranes and upon various critical enzyme functions in these organelles, particularly those such as lipoate-dependent enzymes, involved in energy metabolism; to investigate sulfhydryl and disulfide bonds in muscle and liver of deficient chicks and in those receiving one or more of the nutrients under investigation.